A Solid Oxide Fuel Cell (SOFC) is a device for directly converting the chemical energy of a fuel into electrical energy. Document U.S. Pat. No. 4,943,493 discloses a fuel cell power plant, wherein a hydrocarbon fuel is reformed in a reformer to provide a hydrogen rich fuel stream and the hydrogen rich fuel stream is oxidized in a fuel cell. A stream of anode exhaust and an oxidant stream comprising cathode exhaust and air are combusted in the burner. The fuel cell power plant allows indirect control of the burner flame temperature in that the composition of the oxidant stream are controlled to maintain the oxygen content of the burner exhaust stream within a predetermined range and thus maintain the flame temperature of the combustion mixture within a preferred range.
One disadvantage of this fuel cell power plant is that the control of the combustion in the burner is difficult in view that having a depleted air coming out of the stack at very high flow rate makes the controllability of a complete combustion, which means a combustion that burns all fuel, challenging, especially when the system operates under modulating loads. A further disadvantage is that a relatively large burner is necessary in the system. A further disadvantage is that an external water line and an apparatus for generating steam is necessary to run the system.